Dense breasts mean that a mammogram shows more fibrous and glandular tissue than fatty tissue. BI-RADS breast density categories C (heterogeneously dense) and D (extremely dense) are considered dense.
 
Dense breasts are common and are not abnormal. However, they matter because dense tissue can make some breast cancers harder to see on mammography and is independently associated with increased breast cancer risk.
 

Key Takeaways

• Dense breasts are BI-RADS categories C or D.
• Breast density is assessed on a mammogram, not by breast size, appearance or touch.
• Dense tissue can reduce mammographic sensitivity.
• Ultrasound or MRI is not automatically required; screening should reflect breast density and overall breast cancer risk.

What are dense breasts?
Breasts contain fatty, fibrous and glandular tissue. On a mammogram, fatty tissue appears darker, while fibrous and glandular tissue appear white. A radiologist determines breast density from the mammogram.
 
The BI-RADS system classifies breast density into four categories:
 

Breast density	What it means
A – Almost entirely fatty	Mostly fatty tissue.
B – Scattered areas of fibroglandular density	Some areas of dense tissue are present.
C – Heterogeneously dense	Substantial areas of dense tissue may obscure small masses.
D – Extremely dense	Most of the breast is dense tissue, reducing mammographic sensitivity.

 

Categories C and D are considered dense breasts.
 

Why can dense breasts make mammograms harder to read?
Dense breast tissue and many breast cancers both appear white on a mammogram. This can create a masking effect, making a small abnormality less visible against dense tissue than against darker fatty tissue.
 
Mammography remains an important screening test for women with dense breasts, but density may influence whether additional imaging could be useful.
 

Do dense breasts increase breast cancer risk?
Yes. Higher breast density is an independent breast cancer risk factor, and risk generally increases as density increases.
However, density is only one part of your risk profile. Other factors include age, family history, certain inherited genetic variants, previous high-risk breast lesions and previous chest radiation. Screening decisions should therefore consider overall breast cancer risk rather than breast density alone.
 

Do I need ultrasound or MRI if I have dense breasts?
Not automatically. The best screening approach depends on breast density, overall risk, previous imaging and medical history.
Your doctor may discuss:

• 3D digital mammography or digital breast tomosynthesis: Creates multiple breast images from different angles to help evaluate overlapping tissue.
• Breast ultrasound: May find abnormalities that are difficult to distinguish on mammography, but can also identify findings that ultimately prove benign.
• Breast MRI: May be recommended for women at high risk and considered for selected women with dense breasts.

 
A useful question to ask your doctor is: “Given my breast density and other risk factors, what screening plan is appropriate for me?”
 

Why choose Bumrungrad for breast screening and dense breast assessment?
At Bumrungrad International Hospital, the Breast Center works with the Diagnostic Radiology and Nuclear Medicine Center and Horizon Regional Cancer Center to support breast screening, diagnosis and treatment.
 

• Advanced breast imaging:

Services include digital mammography, breast ultrasound, breast MRI and image-guided breast biopsy when appropriate. Bumrungrad also uses Lunit INSIGHT MMG, an AI-assisted mammography system that supports radiologists by highlighting suspicious regions for closer review.
 

• JCI-certified Breast Cancer Program:

In 2025, Bumrungrad’s Breast Cancer Program received Joint Commission International Clinical Care Program Certification (JCI CCPC).
 

• Global Recognition:

In Newsweek and Statista’s Best Specialized Hospitals Asia Pacific 2026, Bumrungrad ranked No. 1 in Thailand and 58th in Asia-Pacific for Oncology. Bumrungrad also ranked No. 96 worldwide in Newsweek’s World’s Best Hospitals 2026, remaining the only Thai hospital in the global Top 100.


Frequently Asked Questions
Are dense breasts abnormal?
No. Dense breasts describe breast tissue composition; they are not a disease or abnormal condition.
 
Can I tell if I have dense breasts by touch?
No. Breast density is determined from a mammogram by a radiologist.
 
Does having dense breasts mean I will get breast cancer?
No. Dense breasts increase risk, but they do not mean you will develop breast cancer.
 
Should women with dense breasts still have mammograms?
Yes. Mammography remains a core breast cancer screening test. Whether supplemental ultrasound or MRI may help depends on individual risk and clinical circumstances.
 


References

1. Newell MS, Destounis SV, Leung JWT, DeMartini WB, Lee CH, Eby PR. ACR BI-RADS® v2025 Manual. American College of Radiology; 2025.
2. National Cancer Institute. Dense Breasts: Answers to Commonly Asked Questions. Updated December 2025.
3. American College of Radiology. ACR Appropriateness Criteria®: Supplemental Breast Cancer Screening Based on Breast Density.
4. Boyd NF, Guo H, Martin LJ, et al. Mammographic density and the risk and detection of breast cancer. New England Journal of Medicine. 2007;356(3):227–236.
5. Bakker MF, de Lange SV, Pijnappel RM, et al. Supplemental MRI screening for women with extremely dense breast tissue. New England Journal of Medicine. 2019;381(22):2091–2102.
6. Comstock CE, Gatsonis C, Newstead GM, et al. Comparison of abbreviated breast MRI vs digital breast tomosynthesis for breast cancer detection among women with dense breasts undergoing screening. JAMA. 2020;323(8):746–756.

 

Medically reviewed by:
Piyawan Kensakoo, M.D.
Breast Surgery & General Surgery
Last medically reviewed: September 2026